The invention relates to motor vehicles in general, and more particularly to improvements in power transmitting and power transmission interrupting arrangements (hereinafter called power trains) for use in motor vehicles. Still more particularly, the invention relates to improvements in power trains of the type wherein the torque transmitting system (such as a friction clutch or a torque converter with a bypass or lockup clutch) and/or the gear selecting and shifting transmission system is automated.
Power trains of the above outlined character comprise means for operating the automated system or systems. Certain recently developed operating means employ a discrete signal receiving and signal transmitting control unit (such as an electronic circuit) for each automated system, a single control unit for the single automated (transmission or torque transmitting) system, or a common control unit for both automated systems. The connection between a control unit and a discrete automated system or between a control unit and each of two automated systems comprises actuating means for shifting an automated transmission system into or from a selected or particular gear and/or for changing the condition of an automated torque transmitting system between a disengaged or partly or fully engaged condition.
Power trains of the above outlined character are disclosed, for example, in published German patent application Serial No. 43 09 901 (to which reference may be had, if necessary). For example, one of the power trains disclosed in this published German patent application is designed to ensure that shifting of the transmission system into a selected gear and/or any other regulation(s) of the transmission system is or are automated which is in contrast to most standard power trains employing a manually operable transmission system with a lever or rod which must be actuated by the operator of the motor vehicle to select a particular gear, to shift from a previously selected gear and to shift into the newly selected gear.
A drawback of presently known power trains with automated transmission systems and/or with automated torque transmitting systems is that, in the event of a malfunction or breakdown (such as damage to or destruction of an important or key component) and/or under other circumstances which cause a partial or complete failure of the automated system, the operator or even a highly skilled mechanic can be confronted with a situation that the motor vehicle is stalled or stranded at a location which is remote from an acceptable parking area, garage or repair shop. In this respect, a manually operated transmission system or torque transmitting system is more practical because, and assuming that the motor vehicle is equipped with a standard manually shiftable transmission system, exertion of a rather pronounced force upon the gear shifting lever or rod normally suffices to shift the manually operated transmission system into a selected gear or from a particular gear in order to place the motor vehicle in a condition in which the vehicle can be driven to a desired location by its own prime mover, or towed or pushed to such location by the operator (with or without assistance, e.g., from other occupant(s) of the affected vehicle) or by a second vehicle.
Analogously, if a pedal-operated torque transmitting system (such as a friction clutch) happens to malfunction, it is often still possible to cause the clutch to assume an engaged or disengaged condition, depending upon whether the disabled or partially disabled vehicle is to be pushed or pulled to a selected location or advanced to such location under its own power (e.g., at a low or extremely low speed).
If the power train of a motor vehicle employs an automated transmission system which is designed to be shifted into selected gears in response to signals from an electronic control unit, failure of the electrical energy supplying means can entail a disablement of the control unit so that automatic shifting into or from a selected gear is no longer possible. The same undesirable situation arises if a defect develops in the actuating means which is operated by the control unit and normally transmits motion to one or more internal or external mobile gear shifting and/or selecting components of an automated transmission system. Such actuating means can employ one or more electric or other suitable motors and a linkage, a cable, a Bowden wire or other suitable means for transmitting motion from the output element(s) of the motor or motors to the mobile input element(s) of the automated transmission system. Thus, if a malfunction develops .while the automated transmission system is in (a forward or reverse) gear (rather than in neutral), e.g., due to the failure of the car battery and/or a generator to supply electrical energy to the electronic control unit, the transmission system acts as a parking brake and prevents any movements of the affected motor vehicle. The reason is that a conventional automated transmission system cannot be shifted into neutral gear if such automated system and/or the operating means therefor develops certain defects.
Presently known operating means for automated transmission systems are constructed and assembled in such a way that, if a malfunction develops in the means for transmitting signals to a control unit (e.g., a microprocessor) of the operating means or the means for transmitting signals from the output or outputs of the control unit to the driving unit or units (e.g., one or more electric motors) of the actuating means between the control unit and the automated transmission system, the operator of the motor vehicle is no longer in a position to shift the defective automated transmission system into neutral gear or into another (forward or reverse) gear. This results in the aforediscussed inconveniences, such as the inability of the operator of the affected motor vehicle to drive the vehicle to a desired location under its own power, or even to push or pull the vehicle to such location. Thus, it is then necessary to lift the disabled motor vehicle onto the platform of a truck or to actually dismantle certain parts of the power train in order to alter the condition of the power train to an extent which is necessary to permit the driving, pushing or pulling of the vehicle to a safe parking area, to an area which is authorized for parking, to the garage of the owner of the vehicle, or to a repair shop.
The situation is not much different in the event of malfunctioning of an automated torque transmitting system (e.g., a friction clutch or a torque converter with a bypass or lockup clutch) and/or of the means for operating such automated torque transmitting systems. Thus, it is not alway possible to place a disabled automated torque transmitting system into a fully engaged condition, into a partially engaged condition or into a fully disengaged condition.